Topic 12 - Immunology Flashcards
What does the immune system protect from?
- Bacteria
- Viruses
- Parasites
- Fungi
- Tumor cells
What are the two types of immunity the body utilizes?
- Innate Immunity (first defense line, non-specific response)
- Adaptive Immunity (second defense line, highly specific with memory)
How does active immunity work?
- Antigens enter body and trigger
- Innate and adaptive immune systems
- Provides long term protection
How does passive immunity work?
- Antibodies pass from mother to foetus across the placenta/infant through breast milk
- Provides short term protection
Which cell are the cells of the immune system derived from?
Pluripotent hematopoietic stem cell in bone marrow
What are the two lineages?
- Myeloid
- Lymphoid
Which cells does the myeloid lineage generate?
- Polymorphonuclear leukocytes (neutrophil, eosinophil, basophil)
- Monocyte/macrophages
- Dendritic cells
- Mast cells
Which cells does the lymphoid lineage generate?
B- and T- and natural killer lymphocytes
How are Polymorphonuclear leukocytes or granulocytes characterised?
Multilobed (2 to 5) nuclei and cytoplasmic granules
What are the Polymorphonuclear leukocytes?
- Neutrophils
- Eosinophils
- Basophils
- Monocytes
- Macrophages
- Dendritic cells
- Mast cell
What are neutrophils?
Principal phagocytic cell of innate immunity. Rapidly migrate to sites of infection, ingest microbes by phagocytosis, release oxygen free radicals, degranulate releasing proteins with microbicidal properties e.g. lysozyme
What are eosinophils?
Important defender against multicellular parasites and have a role in allergy and asthma.
What are basophils?
Involved in inflammatory allergic reactions. Releases the potent vasodilator, histamine.
What are monocytes?
- Circulate in blood, bean shaped nuclei, precursors of tissue macrophages.
- Effectors of the inflammatory response to microbes.
- Kills pathogens via phagocytosis, free radical production, myeloperoxidase and inflammatory cytokines.
What are macrophages?
- Derived from blood monocytes
- Participate in innate and adaptive immunity
- Phagocytosis, microbicidal mechanisms, antigen presentation to other cells
What are dendritic cells?
Process and present antigens (antigen presenting cell {APC}) on their cell surface to T-lymphocytes to initiate specific immune responses.
What are mast cells?
Similarities with basophils, release histamine, close association with allergy and inflammation
What are the small lymphocytes?
- B lymphocytes
- T lymphocytes
What do B lymphocytes do?
produce antibodies, present antigens to other cells (APC), can produce long lived memory cells
What do T lymphocytes do?
Part of innate immune response. Plays critical role in development and regulation of cell mediated immunity. Influences the activities of other cells (e.g. B-cells), able to kill virally infected and tumour cells, generate long lived memory cells
What do Natural Killer cells do?
Release perforins and granzymes and trigger apoptosis in target cell.
Kill infected cells which do not express foreign surface antigen, respond rapidly, involved in tumour immunosurveillance.
What are the key immunological sites in the body?
- Primary lymphoid tissue
- Secondary lymphoid tissue
What happens at the primary lymphoid tissue?
Development and maturation of lymphocytes :
- bone marrow (B lymphocytes)
- thymus gland (T lymphocytes)
What happens at the secondary lymphoid tissue?
Mature lymphocytes encounter antigens/pathogens:
Includes: lymph nodes, spleen and lymphoid tissue at other sites e.g. tonsils, appendix, adenoids, Peyer’s patches (in ileum),bronchial associated lymphoid tissue (BALT).
Which sites on the body are lymph nodes found at?
- Jaw
- Neck
- Axilla
- Elbow crease
- Groin
- Behind the knee
What happens at the lymph nodes during infection?
Virgin B- and T-lymphocytes home from
bone marrow and thymus to specific sites in lymph nodes. Architecture and
size of nodes change in response to activation and proliferation of lymphocytes
What are the components of the spleen?
-Red pulp
(Erythrocytes removed)
-White pulp
(Lymphocytes stimulated)
What is the spleen?
- Lymphoid organ in the abdomen
- Removes damaged or old erythrocytes
- Key site of activation of lymphocytes from blood borne pathogens
What are the key components of the innate immune system?
- Mechanical barriers
- Physiological
- Chemical mediators including circulating plasma proteins
- Phagocytic leukocytes
- Natural Killer cells
What are the mechanical barriers of the innate immune system?
Provided by skin and mucous membranes, competition with normal flora, mucous entraps, and cilia propel microbes out of body.
What are the physiological components of the innate immune system?
Stomach acid kills some pathogens; fever response inhibits pathogen growth
What are the chemical mediators of the innate immune system?
- Lysozyme cleaves bacterial cell wall
- Interferon induces antiviral defenses in uninfected cells
- Complement lyses microbes directly or facilitates phagocytosis
What are the phagocytic leukocytes?
- Phagocytes
- Macrophages
- Neutrophils
What is the purpose of macrophages?
Reside in tissues and recruit neutrophils, become activated release cytokines (TNF, IL1)
What is the purpose of neutrophils?
Enter infected tissues in large numbers, become activated, release cytokines (TNF), phagocytose bacteria
What do Natural Killer cells do?
- Summoned from the blood
- Release cytokines (IFN-γ, IL2)
- Kill infected cells (trigger apoptosis)
What is the adaptive immune system?
- Called into action when pathogens overcome innate immune defense
- Activates, proliferates, and creates specific responses to eliminate microbe
What are the two types of adaptive immune responses?
- Humoral immunity (antibodies produced by B lymphocytes)
- Cell-mediated immunity (T lymphocytes)
What is the function of resident macrophages in non-infected tissue?
Eating up dead and dying cells in the tissue.
What is the function of dendritic cells in non-infected tissue?
On sentry duty waiting for the first sign of a pathogen.
